diff --git a/camera/provider/default/ExternalCameraProvider.cpp b/camera/provider/default/ExternalCameraProvider.cpp
index d47ddbf..4d2c847 100644
--- a/camera/provider/default/ExternalCameraProvider.cpp
+++ b/camera/provider/default/ExternalCameraProvider.cpp
@@ -46,7 +46,7 @@
 constexpr char kDevicePath[] = "/dev/";
 constexpr char kPrefix[] = "video";
 constexpr int kPrefixLen = sizeof(kPrefix) - 1;
-constexpr int kDevicePrefixLen = sizeof(kDevicePath) + kPrefixLen + 1;
+constexpr int kDevicePrefixLen = sizeof(kDevicePath) + kPrefixLen - 1;
 
 bool matchDeviceName(int cameraIdOffset, const std::string& deviceName, std::string* deviceVersion,
                      std::string* cameraDevicePath) {
@@ -379,4 +379,4 @@
 }  // namespace provider
 }  // namespace camera
 }  // namespace hardware
-}  // namespace android
\ No newline at end of file
+}  // namespace android